The general aim of the proposed research is to obtain estimates, based on self reports and urine tests, of the prevalence of illicit drug use among "intermediate populations" of traffic and minor offenders. These populations have not been targeted or adequately covered by existing general population surveys or surveys of criminal justice populations. Traffic and minor offenders comprise the bulk of the arrestee population. Their drug use poses problems for law enforcement agencies and the public, and therefore requires systematic measurement that is not included in current drug use indicators. Results from this research will provide a basis for reconciling disparate drug use prevalence estimates from offender and general population samples. The research also will permit comparisons of drug use patterns across a broad spectrum of the arrestee population. Two important components of the project are (1) to assess the validity of self-report indicators of drug use by comparing them with the results of urine tests and (2) to generate reliable estimates of drug use, and its sociodemographic and behavioral correlates, for more representative samples of arrestees. The drug use and sociodemographic data required to address these research issues will be obtained from a representative sample of 2,600 ordinance violators and traffic offenders interviewed at the central booking facility of the St. Louis Metropolitan Police Department. Subjects will also be asked to provide urine specimens for drug testing. The results of this research can assist law enforcement officials and criminal justice policy-makers in more accurately targeting pretrial treatment, prevention, and enforcement efforts. The methods and findings should also provide a basis for other researchers to further examine the utility of using multiple indicators in detecting drug use among persons detained by the criminal justice system.